9th Lesson Microbiology PDF

# Medical Mycology ## Summary - This chapter discusses the classification of fungi in relation to host cells, the classification of mycoses, and the vegetative and reproductive structures of fungi. - It also covers the growth and nutrition of fungi. - Key fungal species discussed include *Dermatoph...

# Medical Mycology ## Summary - This chapter discusses the classification of fungi in relation to host cells, the classification of mycoses, and the vegetative and reproductive structures of fungi. - It also covers the growth and nutrition of fungi. - Key fungal species discussed include *Dermatophytes*, *Mycetoma*, *Histoplasmosis*, and *Cryptococcosis*, focusing on pathogenesis, clinical features, and laboratory diagnosis. ## Evaluation ### Multiple Choice Questions 1. The father of Medical Mycology is **Raymond Jacques Sabouraud**. 2. **Systemic** is an example of deep mycoses. 3. **Aistoplasma** is an example of dimorphic fungi. 4. Phaeoid fungi is also called **Black yeast**. 5. Tinea Barbae is also called **Barber's itch**. 6. Tear-shaped micro conidia are found in **T. mentagrophytes**. 7. **Piedra** is called as "Madura foot" disease. 8. **Mycetoma** is known as "Darling's disease". 9. Diaper rash is caused by **Candidiasis**. 10. Demonstration of **Germ tube** is called as Reynolds-Braude phenomenon. ### Answer the Following 1. Mycology is the branch of biology that deals with the study of fungi. 2. Host parasitic relationship is based on how the fungus interacts with the host. There are three types: * **Commensalism:** The fungus neither benefits nor is harmed by the host. * **Mutualism:** The fungus benefits from the host. * **Parasitism:** The host is harmed by the fungus. ## Mycology - The branch of biology that deals with the study of fungi is **Mycology**. - "Mycology" is derived from the Greek words `Mykes`, which means **mushroom**, and `Logos`, which means **study**. - **Medical Mycology** is the study of fungal infection, epidemiology, ecology, pathogenesis, diagnosis, and treatment in human beings. - **Raymond Jacques Sabouraud** (1864-1936) is the father of Medical Mycology. ### Classification of Fungi Based on Host Parasitic Relationships - Fungi are grouped into three types based on how they interact with their host: * **Commensalism:** The fungus neither benefits nor is harmed by the host. * **Mutualism:** The fungus benefits from the host. * **Parasitism:** The host is harmed by the fungus. ### Mycoses - Mycoses are diseases caused by medically important fungi. - They are categorized into: * **Pathogenic fungi**: Fungi that adapt to skin flora and cause infection. * **Opportunistic fungi**: Fungi that cause infection when the host's immune system is weakened. * **Toxigenic fungi**: Fungi that produce toxins responsible for illness or death after ingesting contaminated food. * **Allergenic fungi**: Fungi that secrete allergens that cause allergic reactions. ### Mycoses Classifications Based on Location - Mycoses are classified according to their location: * **Superficial Mycoses**: These infections are limited to the outer layers of the skin and its appendages. Example: *Malassezia* and *Piedra*. * **Cutaneous Mycoses**: These infections extend deeper into the epidermis and also invade hair and nails. Example: *Dermatophytes*. * **Subcutaneous Mycoses**: These infections extend to dermis, subcutaneous tissue, and muscles by any traumatic injury. Example: *Mycetoma*. * **Systemic Mycoses**: These infections originate from lungs and later spread systemically to other organs. Systemic fungal infections are known as deep mycoses. Example: *Cryptococcosis*. * **Opportunistic Mycoses**: These infections occur when the immune status of the individuals is altered. Example: *Candidiasis*. ### Aeromycology - The study of air-borne fungi, their types, and the seasonal variations of allergenic fungal spores in the environment is called **Aeromycology**. - Certain fungal pathogens cause infections associated with workers in mycological laboratories. - To avoid this, safety procedures, equipment, and bio-safety levels (BSL) are used. BSL-1 is for low-risk microorganisms, and BSL-4 is for highly risk pathogens. ### Vegetative Structures -Vegetative structures are formed by the vegetative mycelia that have no reproductive value, but are important for the differentiation of fungi. - Examples include **Chlamydospores** and **Arthrospores**. - Chlamydospores are thick-walled, resistant to adverse conditions, and are larger than other cells. - Arthrospores are rectangular spores that are thick-walled and are dispersed on maturity. ### Reproduction of Fungi - Spores play a major role in fungi reproduction. - Reproduction can be either asexual or sexual: * **Asexual Reproduction:** Fungi reproduce by budding, fission, or mitosis, resulting in the production of microspores (microconidia) and macrospores (macroconidia). * **Sexual Reproduction:** This process consists of: * **Plasmogamy**: The fusion of cytoplasm. * **Karyogamy**: The fusion of two nuclei. * **Meiosis**: The formation of haploid cells. - The two phases of sexual reproduction are **Anamorphs** and **Telomorphs**. ### Mycelia Sterile - Mycelia Steriles are fast-growing molds that do not produce spores or conidia. - They are medically significant fungi and are difficult to identify. ### Dermatophytoses - Dermatophytoses are the most common cutaneous fungal infections in humans and animals, affecting skin, hair, and nails. - They are also known as **Tinea** or **ringworm**. - Dermatophytes are a group of hyaline septate fungi that invade keratinized tissues of the skin and appendages. - They produce keratinolytic proteases, enabling them to invade living cells. - Fungal metabolic products are responsible for erythema, vesicles, and pustules at the site of infection. - Some dermatophytes species, such as soil saprobes, can digest keratin debris in soil and can parasitize keratinous tissues of animals. ### Clinical Features of Dermatophytoses - Dermatophytoses, also known as **Tinea** or **Ringworm**, are classified according to the anatomical site involved. - Common presentations of dermatophytoses include: * **Tinea Capitis**: Infection of the scalp, causing hair loss and inflammation. * **Tinea Corporis**: Infection of the non-hairy skin, causing ringworm. * **Tinea Imbricata**: Infection of the glabrous skin with concentric rings with intense scaling. * **Tinea Gladiatorum**: Infection that occurs primarily in wrestlers and athletes. * **Tinea Faciei**: Infection of the face, causing annular plaques. * **Tinea Barbae**: Infection of the beard and moustache area. * **Tinea Pedis**: Infection of the foot, also known as "Athlete’s foot". * **Tinea Cruris**: Infection of the groin. * **Tinea Manuum**: Infection of the palms of the hands. * **Tinea Unguium**: Infection of the fingernails. ### Microscopic and Macroscopic Features of Dermatophytes - Dermatophytes are characterized by their microscopic and macroscopic features: * **Trichophyton**: Numerous thin-walled, smooth macroconidia and abundant microconidia. * **Microsporum**: Numerous thick-walled, rough macroconidia and rare microconidia. * **Epidermophyton**: Numerous smooth-walled macroconidia and NO microconidia. ### Mycetoma - **Mycetoma** is a slowly progressive, chronic granulomatous infection of the skin and subcutaneous tissues. - It typically involves underlying fascia and bones, often affecting the extremities. - Also referred to as **Madura foot** or **Maduramycosis**. #### Classification of Mycetoma - Mycetoma is classified based on the causative agent: * **Aerobic Actinomycetes**: Cause **Actinomycetoma**. * **Hyaline and Phaeoid fungi**: Cause **Eumycetoma**. ### Clinical Features of Mycetoma - Mycetoma can present with a range of symptoms, including: * **Swelling and abscess formation**: In the affected area. * **Drainage**: Of pus, which may contain granules. * **Pain**: In the affected area. * **Bone involvement**: Which can lead to bone erosion. ### Systemic Mycoses - Systemic mycoses are caused by dimorphic fungi and are typically acquired by inhalation of spores. - These infections primarily involve the respiratory system but can spread to other parts of the body through circulation. - They are caused by **true fungal pathogens**. - Systemic mycoses include: * **Histoplasmosis**: Caused by *Histoplasma capsulatum*, a dimorphic fungus. * **Blastomycosis**: Caused by *Blastomyces dermatitidis*, a dimorphic fungus. ### Histoplasmosis - Histoplasmosis is caused by the dimorphic fungus *Histoplasma capsulatum*. - The fungus lives inside macrophages and giant cells, where it grows within the reticuloendothelial system. - It is also known as **Darling's disease**. ### Pathogenesis and Pathology of Histoplasmosis - The infection with *H. capsulatum* begins when conidia or mycelial fragments are inhaled and converted into yeasts in alveolar macrophages. - The yeast cells parasitize macrophages and are activated by lymphocytes, leading to localized granulomatous inflammation. ### Clinical Features of Histoplasmosis - The disease is often asymptomatic, but when symptomatic, the severity of symptoms depends on the intensity of exposure to conidia and the host's immune response. - Histoplasmosis can present with: * **Acute Pulmonary Histoplasmosis**: Fever, headache, chills, sweating, chest pain, cough, and dyspnea. * **Chronic Pulmonary Histoplasmosis**: Ulcerative lesions of the lips, mouth, nose, larynx and intestines. * **Cutaneous Mucocutaneous Histoplasmosis**: Mucous lesions on skin, abdomen wall, and thorax. * **Disseminated Histoplasmosis**: Fever, anoxia, anemia, leucopenia, hepatosplenomegaly, and multiple lymphadenopathies. ### Laboratory Diagnosis of Histoplasmosis - Samples collected for diagnosis include sputum, bone marrow, lymph nodes, cutaneous and mucosal lesions, and peripheral blood film - Methods for diagnosis include: * **Direct examination**: Examining thick and thin smears stained with Calcofluor white, Giemsa, or Wright stains. The fungus appears as small, oval, yeast-like cells, 2-4 µm in diameter, within the mononuclear or polymorph nuclear cells and occasionally in giant cells. * **Fungal culture**: Culturing specimens on Sabouraud dextrose agar (SDA) with antibiotics and incubating at 25 or 37 degrees Celsius. Colonies are observed in 3-4 days and appear cream colored, smooth, and pasty. ### Opportunistic Mycoses - Opportunistic mycoses are infections found in patients with underlying predisposing conditions. - They are caused by non-pathogenic or contaminant fungi in a host where the immunological defense mechanisms are weakened due to endogenous causes (such as cancer or leukemia) or exogenous causes (like immunosuppressive therapy or AIDS). - Examples include: * **Candidiasis** * **Cryptococcosis** * **Aspergillosis** * **Zygomycosis** ### Candidiasis - Candidiasis is a fungal infection caused by different species of Candida. - The most common species is *Candida albicans*. - Candidiasis can affect various parts of the body, including the skin, mouth, vagina, and esophagus. - It is mainly a result of an overgrowth of Candida in the body, which can happen due to factors such as: * **Weakened immune system**. * **Hormonal changes**. * **Antibiotic use**. * **Diabetes**. ### Clinical Features of Candidiasis - Candidiasis can present with different clinical features, depending on the affected body part. - These include: * **Oral Candidiasis**: White patches or plaques on the tongue and inside the mouth. It’s often called thrush. * **Vaginal Candidiasis**: Itching, burning, redness, and discharge. * **Cutaneous Candidiasis**: Itching, redness, and scaling. * **Esophageal Candidiasis**: Pain when swallowing. ### Laboratory Diagnosis of Candidiasis - Samples collected for diagnosis include oral and vaginal swabs, blood samples, and tissue biopsies. - Methods for diagnosis include: * **Direct examination**: Examining smears stained with Gram stain or KOH. Yeast cells and pseudohyphae are observed. * **Fungal culture**: Culturing specimens on Sabouraud dextrose agar (SDA) with antibiotics and incubating at 25 or 37 degrees Celsius. Colonies are observed in 3-4 days and appear cream colored, smooth, and pasty. * **Germinated tube test**: This special test involves treating the fungal culture with normal human serum and then incubating it at 37 degrees Celsius. The presence of germ tubes confirms the presence of Candida species. ### Cryptococcosis - Cryptococcosis is an acute, sub-acute, or chronic fungal disease caused by the encapsulated yeast *Cryptococcus neoformans*. - It is pathogenic in animals and humans. - It is a common cause of opportunistic infections, particularly in people with weakened immune systems. ### Pathogenesis and Pathology of Cryptococcosis - The infection usually begins with inhalation of small, airborne basidiospores. - The *Cryptococcus neoformans* may remain dormant in the lungs until the immune system weakens. - It can then disseminate to the central nervous system and other body sites. ### Clinical Features of Cryptococcosis - Cryptococcosis can present with a range of symptoms, depending on the affected body site. - These include: * **Pulmonary Cryptococcosis**: Cough, chest pain, and fever. * **Meningoencephalitis**: Headache, fever, stiff neck, confusion, and altered mental status. * **Skin Cryptococcosis**: Skin lesions, often with a characteristic white or pink appearance. * **Visceral Cryptococcosis**: Spread of infection to other organs, such as the liver, spleen, kidneys, and bones. ### Laboratory Diagnosis of Cryptococcosis - Samples collected for diagnosis include cerebrospinal fluid (CSF), blood, sputum, urine, and tissue biopsies. - Methods for diagnosis include: * **Direct examination**: Examining smears of CSF, blood, or tissue stained with India ink or Calcofluor white. * **Fungal culture**: Culturing specimens on Sabouraud dextrose agar (SDA) with antibiotics and incubating at 25 or 37 degrees Celsius. Colonies are observed in 3-4 days and appear mucoid or creamy white. * **Latex agglutination test**: A rapid test used to detect the presence of cryptococcal antigen in CSF or serum. * **Cryptococcal antigen test**: A more sensitive test than the latex agglutination test, also used to detect cryptococcal antigen in CSF or serum. ### Cryptococcal Meningitis - Cryptococcal meningitis can be caused by *Cryptococcus neoformans* or * Cryptococcus gattii * - * C. gattii* is rare in healthy people and is mostly seen in immunocompromised people. **Important Notes:** * The document provided contains information about the diseases caused by fungi and their classification, diagnosis, and treatment. * The document mentions the importance of safety precautions and hygiene habits to avoid fungal infections. * The document contains information on the structure and reproduction of fungi. * The document also includes information on the clinical features, diagnosis, and treatment of various fungal infections. * The document emphasizes the importance of early diagnosis and treatment to prevent the spread of fungal infections.